$100 Bounty - Charge in Dual Currency

Hi

I need to be able to charge my users in the following way

User From India - INR
User From Rest of the World - Show Price and Charge in USD

I am looking for a solution for this problem and would like to open source this solution for others as well who might be looking for variations of this.

$100 Bounty to be paid to anyone who can give me a working solution for this !
Thanks